黄河三角洲潮滩的侵蚀和再沉积:示踪砂棒法的应用

Erosion and redeposition in tidal flats of the Yellow River delta: Result of tracer stick monitoring

利用示踪棒方法，对现代黄河三角洲潮滩的半年和整年的再沉积进行了定量测量，分析了潮滩沉积动力的影响因素。测量结果显示，尽管潮滩地形平均变化值只有1cm左右，但是平均沉积交换量（侵蚀和再沉积之和）是它的10倍。因此，潮滩地形处于基本稳定状态，但是无论是北侧还是南侧潮滩，都存在强烈的物质交换。对比结果表明，北侧潮滩沉积交换最强，且主要发生在下半年。北侧潮滩每年的沉积交换量为15-33cm。南侧潮滩沉积交换量次于北侧潮滩，上半年和下半年的沉积交换量相当。东侧潮滩沉积交换最弱。影响沉积交换和再沉积的原因包括海洋动力、河流输沙、局部地形特征、海滩植被、海滩蟹类活动、人工突堤等，此外气候（冰冻）也影响北侧潮滩沉积交换。

In estimating the sedimentological and morphological evolution of tidal flat, it is essential to know the quantity of redepo-sition. The knowledge is also helpful to understanding the behavior of tidal flat as the transitional zone for nutrient and harmful sub-stances （e.g., heavy metals）. A method“tracer stick method”was applied to collecting data about erosion and accumulation with an accuracy of millimeters. The results show that the annual morphological change in these tidal flats is about one centimeter, but the sediment turnover is almost a magnitude larger. The highest sediment mobility happens in the north tidal flat of the modern Yellow River, because it suffers stronger wave and tidal currents, and it is close to the current river mouth and is affected subsequently by the sediment discharge of the river. The sediment mobility becomes weak during the frozen period between December and March. The south tidal flat also has significant sediment mobility, with the sediment turnover being 5-10cm. A man-made dyke for oil produc-tion shelters the east tidal flat and, as a result, the tidal flat has the small sediment mobility.